abar121 said:
Beedub said:
the block was iron for a reason.... means a very strong engine structurally.... perfect for high revs and BOOOOSSSTT... its the german 2jz.
Unless someone knows otherwise
I think otherwise :wink:
It's historical.
The s54 is off course a development from the s50 (it's virtually the same block/crank) which is based on the M50. An engine introduced in 1990.
In that time, aluminium engines were rather exotic.
When the m50 went out of production (1996) the all aluminium m52 was introduced (1994), but the s50 stayed for the m3. (the s50b32 was back then even much more ahead from the competition as the s54 was in its days; think of it: 320hp in 1996!)
The m52 went on becoming m52TU and finally m54. The m52/m54 block was probably designed for 3L max. The m54 is iron sleeved, and bmw probably doesn't dare to bore it 3mm extra to get to 3,2Liters. It has to cope with 'factory reliability', in contrast to tuners. So the cast iron block has more 'meat' to bore to a bigger displacement.
High revs is not something that really stresses the block, it's torque. Looking at the n54, with turbo, being open deck (m54 is closed deck, so even stronger) means that aluminium in itself is strong enough.
The s65 and s85 (bmw's best engine

) are also full aluminium, and reliable under boost. (a cast iron V10 might get a bit heavy also...)
So I think that's how it went.